Traditionally, as methods for measuring the concentrations of an antigen or antibody, methods of labeling an antigen or antibody with a radioisotope or enzyme have been used, but these methods have problems in aspects such as sensitivity and safety; therefore, in place of these methods, various methods of labeling an antigen or antibody with a fluorescent dye, and measuring the concentration of the antigen or antibody therewith have been studied.
For example, Japanese Patent Laid-Open No. 501873/1984 (U.S. Pat. No. 4,582,809) etc., describe a method comprising the steps of binding an antigen or antibody to a side surface of an optical fiber; immunologically reacting an antibody or antigen labeled with a fluorescent dye on this optical fiber surface; an excitation light to the optical fiber, thereby exciting the fluorescent dye on the optical fiber; reflecting this fluorescence on the outgoing end surface of the optical fiber; taking out the fluorescence and residual excitation light from the incident end surface of the optical fiber; spectrally splitting them via a beam splitter; and measuring the fluorescence alone (see instant FIG. 4).
However, in the art described above, when attempts of size reduction, cost reduction and sensitivity improvement for practical application were made, the problems shown below have arisen.
Problems have arisen such as 1) to provide a reflective function, processing for forming a reflector on the tip of the optical fiber is necessary, making the cost high; 2) since a reflective function is provided, excitation light mingles in with fluorescence, and a cutoff filter for cutting excitation light is necessary; 3) when the output-power of the light source is increased for sensitivity improvement, excitation light which cannot be removed with the cutoff filter becomes a background; 4) the optical system is complicated and optical axis adjustment is difficult, thus making it difficult to reduce its size.
As stated above, in the prior art, there has been no immunological analyzer which is safe and which permits size reduction, cost reduction and sensitivity improvement, the same being essential to practical application.